In networks based on Code Division Multiple Access (CDMA), several user equipments (UE) can share a same frequency band, by associating to each user equipment a unique code having specific properties. The distinction between the different user equipments is made by detecting the code used by each user equipment.
In such systems, the maximum data rate that can be transmitted is limited by available radio resources, such as the number of available codes and the available transmit power.
Other factors of limitation stem from transport resources in the terrestrial network.
Other limitations are due to the fact that the maximum data rate that can be received/transmitted by a user equipment is limited, or the processing capabilities in the user equipment (e.g. bandwidth, number of simultaneously received codes, etc.) are limited.
A universal mobile telecommunication system (UMTS) is a third generation mobile communication system that has evolved from a European standard known as Global System for Mobile communications (GSM). The UMTS aims to provide improved mobile communication service based on a GSM core network and wideband code division multiple access (W-CDMA) wireless connection technology.
In December 1998, ETSI of Europe, ARIB/TTC of Japan, T1 of the United States, and TTA of Korea formed a Third Generation Partnership Project (3GPP) for creating the detailed specifications of the UMTS technology.
Within the 3GPP, in order to achieve rapid and efficient technical development of the UMTS, five technical specification groups (TSG) have been created for performing the standardization of the UMTS by considering the independent nature of the network elements and their operations.
Each TSG develops, approves, and manages the standard specification within a related region. Among these groups, the radio access network (RAN) group (TSG-RAN) develops the standards for the functions, requirements, and interface of the UMTS terrestrial radio access network (UTRAN), which is a new radio access network for supporting W-CDMA access technology in the UMTS.
FIG. 1 illustrates an exemplary basic structure of a general UMTS network. As shown in FIG. 1, the UMTS is roughly divided into a mobile terminal (or user equipment: UE) 10, a UTRAN 100, and a core network (CN) 200.
The UTRAN 100 includes one or more radio network sub-systems (RNS) 110, 120. Each RNS 110, 120 includes a radio network controller (RNC) 111, and a plurality of base stations or Node-Bs 112, 113 managed by the RNC 111. The RNC 111 handles the assigning and managing of radio resources, and operates as an access point with respect to the core network 200.
The Node-Bs 112, 113 receive information sent by the physical layer of the terminal through an uplink, and transmit data to the terminal through a downlink. The Node-Bs 112, 113, thus, operate as access points of the UTRAN 100 for the terminal.
A primary function of the UTRAN 100 is forming and maintaining a radio access bearer (RAB) to allow communication between the terminal and the core network 200. The core network 200 applies end-to-end quality of service (QoS) requirements to the RAB, and the RAB supports the QoS requirements set by the core network 200. As the UTRAN 100 forms and maintains the RAB, the QoS requirements of end-to-end are satisfied. The RAB service can be further divided into an Iu bearer service and a radio bearer service. The Iu bearer service supports a reliable transmission of user data between boundary nodes of the UTRAN 100 and the core network 200.
The core network 200 includes a mobile switching center (MSC) 210 and a gateway mobile switching center (GMSC) 220 connected together for supporting a circuit switched (CS) service, and a serving GPRS support node (SGSN) 230 and a gateway GPRS support node (GGSN) 240 connected together for supporting a packet switched (PS) service.
The services provided to a specific terminal are roughly divided into the circuit switched (CS) services and the packet switched (PS) services. For example, a general voice conversation service is a circuit switched service, while a Web browsing service via an Internet connection is classified as a packet switched (PS) service.
For supporting circuit switched services, the RNCs 111 are connected to the MSC 210 of the core network 200, and the MSC 210 is connected to the GMSC 220 that manages the connection with other networks.
For supporting packet switched services, the RNCs 111 are connected to the SGSN 230 and the GGSN 240 of the core network 200. The SGSN 230 supports the packet communications going toward the RNCs 111, and the GGSN 240 manages the connection with other packet switched networks, such as the Internet.
Various types of interfaces exist between network components to allow the network components to transmit and receive information to and from each other for mutual communication therebetween. An interface between the RNC 111 and the core network 200 is defined as an Iu interface. In particular, the Iu interface between the RNCs 111 and the core network 200 for packet switched systems is defined as Iu-PS, and the Iu interface between the RNCs 111 and the core network 200 for circuit switched systems is defined as Iu-CS.
FIG. 2 illustrates a structure of a radio interface protocol between the terminal and the UTRAN according to the 3GPP radio access network standards.
As shown in FIG. 2, the radio interface protocol has horizontal layers comprising a physical layer, a data link layer, and a network layer, and has vertical planes comprising a user plane (U-plane) for transmitting user data and a control plane (C-plane) for transmitting control information.
The user plane is a region that handles traffic information of the user, such as voice or Internet protocol (IP) packets, while the control plane is a region that handles control information for an interface of a network, maintenance and management of a call, and the like.
The protocol layers in FIG. 2 can be divided into a first layer (L1), a second layer (L2), and a third layer (L3) based on three lower layers of an open system interconnection (OSI) standard model. Each layer will be described in more detail as follows.
The first layer (L1), namely, the physical layer, provides an information transfer service to an upper layer by using various radio transmission techniques. The physical layer is connected to an upper layer called a medium access control (MAC) layer, via a transport channel. The MAC layer and the physical layer send and receive data with one another via the transport channel.
The second layer (L2) includes a MAC layer, a radio link control (RLC) layer, a broadcast/multicast control (BMC) layer, and a packet data convergence protocol (PDCP) layer.
The MAC layer provides an allocation service of the MAC parameters for allocation and re-allocation of radio resources. The MAC layer is connected to an upper layer called the radio link control (RLC) layer, via a logical channel.
Various logical channels are provided according to the kind of transmitted information. In general, when information of the control plane is transmitted, a control channel is used. When information of the user plane is transmitted, a traffic channel is used. A logical channel may be a common channel or a dedicated channel depending on whether the logical channel is shared. Logical channels include a dedicated traffic channel (DTCH), a dedicated control channel (DCCH), a common traffic channel (CTCH), a common control channel (CCCH), a broadcast control channel (BCCH) and a paging control channel (PCCH) or a Shared Channel Control Channel (SHCCH). The BCCH provides information including information utilized by a terminal to access a system. The PCCH is used by the UTRAN to access a terminal.
A Multimedia Broadcast/Multicast Service (MBMS or MBMS service) refers to a method of providing streaming or background services to a plurality of UEs using a downlink-dedicated MBMS radio bearer that utilizes at least one of point-to-multipoint and point-to-point radio bearer. One MBMS service includes one or more sessions and MBMS data is transmitted to the plurality of terminals through the MBMS radio bearer only while the session is ongoing.
As the name implies, an MBMS may be carried out in a broadcast mode or a multicast mode. The broadcast mode is for transmitting multimedia data to all UEs within a broadcast area, for example the domain where the broadcast is available. The multicast mode is for transmitting multimedia data to a specific UE group within a multicast area, for example the domain where the multicast service is available.
For purposes of MBMS, additional traffic and control channels exist. For example, an MCCH (MBMS point-to-multipoint Control Channel) is used for transmitting MBMS control information while an MTCH (MBMS point-to-multipoint Traffic Channel) is used for transmitting MBMS service data.
The different logical channels that exist are listed below:

The MAC layer is connected to the physical layer by transport channels and can be divided into a MAC-b sub-layer, a MAC-d sub-layer, a MAC-c/sh sub-layer, and a MAC-hs sub-layer according to the type of transport channel to be managed.
The MAC-b sub-layer manages a BCH (Broadcast Channel), which is a transport channel handling the broadcasting of system information. The MAC-d sub-layer manages a dedicated channel (DCH), which is a dedicated transport channel for a specific terminal. Accordingly, the MAC-d sub-layer of the UTRAN is located in a serving radio network controller (SRNC) that manages a corresponding terminal, and one MAC-d sub-layer also exists within each terminal (UE).
The MAC-c/sh sub-layer manages a common transport channel, such as a forward access channel (FACH) or a downlink shared channel (DSCH), which is shared by a plurality of terminals, or in the uplink the Random Access Channel (RACH). In the UTRAN, the MAC-c/sh sub-layer is located in a controlling radio network controller (CRNC). As the MAC-c/sh sub-layer manages the channel being shared by all terminals within a cell region, a single MAC-c/sh sub-layer exists for each cell region. Also, one MAC-c/sh sub-layer exists in each terminal (UE). Referring to FIG. 3, possible mapping between the logical channels and the transport channels from a UE perspective is shown. Referring to FIG. 4, possible mapping between the logical channels and the transport channels from a UTRAN perspective is shown.
The RLC layer supports reliable data transmissions, and performs a segmentation and concatenation function on a plurality of RLC service data units (RLC SDUS) delivered from an upper layer. When the RLC layer receives the RLC SDUs from the upper layer, the RLC layer adjusts the size of each RLC SDU in an appropriate manner upon considering processing capacity, and then creates certain data units with header information added thereto. The created data units are called protocol data units (PDUs), which are then transferred to the MAC layer via a logical channel. The RLC layer includes a RLC buffer for storing the RLC SDUs and/or the RLC PDUs.
The BMC layer schedules a cell broadcast message (referred to as a CB message, hereinafter) received from the core network, and broadcasts the CB messages to terminals located in a specific cell(s). The BMC layer of the UTRAN generates a broadcast/multicast control (BMC) message by adding information, such as a message ID (identification), a serial number, and a coding scheme to the CB message received from the upper layer, and transfers the BMC message to the RLC layer. The BMC messages are transferred from the RLC layer to the MAC layer through a logical channel, i.e., the CTCH (Common Traffic Channel). The CTCH is mapped to a transport channel, i.e., a FACH, which is mapped to a physical channel, i.e., a S-CCPCH (Secondary Common Control Physical Channel).
The PDCP (Packet Data Convergence Protocol) layer, as a higher layer of the RLC layer, allows the data transmitted through a network protocol, such as an IPv4 or IPv6, to be effectively transmitted on a radio interface with a relatively small bandwidth. To achieve this, the PDCP layer reduces unnecessary control information used in a wired network, namely, a function called header compression can be used.
A radio resource control (RRC) layer is located at a lowermost portion of the L3 layer. The RRC layer is defined only in the control plane, and handles the control of logical channels, transport channels, and physical channels with respect to setup, reconfiguration, and release or cancellation of radio bearers (RBs). The radio bearer service refers to a service provided by the second layer (L2) for data transmission between the terminal and the UTRAN. In general, the setup of the radio bearer refers to the process of defining the characteristics of a protocol layer and a channel required for providing a specific data service, as well as respectively setting detailed parameters and operation methods.
The RLC layer can belong to the user plane or to the control plane depending upon the type of layer connected at the upper layer of the RLC layer. That is, if the RLC layer receives data from the RRC layer, the RLC layer belongs to the control plane. Otherwise, the RLC layer belongs to the user plane.
The different possibilities that exist for the mapping between the radio bearers and the transport channels are not always possible. The UE/UTRAN deduces the possible mapping depending on the UE state and the procedure that the UE/UTRAN is executing. The different states and modes are explained in more detail below.
The different transport channels are mapped onto different physical channels. For example, the RACH transport channel is mapped on a given PRACH, the DCH can be mapped on the DPCH, the FACH and the PCH can be mapped on the S-CCPCH, the DSCH is mapped on the PDSCH and so on. The configuration of the physical channels is given by an RRC signaling exchange between the RNC and the UE.
In UMTS systems, it is possible to include Quality of Service (QoS) attributes for a given Packet Data Protocol (PDP) context or Radio Access Bearer (RAB), based on a service profile. The service profiles include Quality of Service (QoS) for conversational traffic, streaming traffic, interactive traffic or background traffic. The service profiles comprise Quality of Service attributes, such as delay attributes, and guaranteed or maximal bit rate. Therefore it is necessary that the network in order to determine whether a given Quality of Service (QoS) can be provided, estimates the resources that will be used by a user equipment, and compares it to the resources that are actually available. This procedure is commonly called RAC (Radio Admission Control) or CAC (Call Admission Control), depending on whether this procedure is done at the beginning of a call, service or at establishment of a new flow, at transition to an active state or during a handoff.
The admission control procedure is triggered each time a link between a user equipment and a given cell must be established.
In UMTS networks, admission control procedure is performed by a Radio Network Controller (RNC). The Radio Network Controller (RNC) can estimate resources that are necessary on the basis of different data provided on one hand by the user equipment (UE) and on the other hand data provided by connected base stations (Node Bs) of the network.
The data provided to the Radio Network Controller by the user equipment can include a Received Energy per chip divided by the power density in the band (Fc/No), a Received Signal Code Power (RSCP), a Received Signal Strength Indicator (RSSI) and a pathloss measured by the user equipment on Common Pilot CHannel (CPICH) of the cell.
The data provided by a connected Node B can include Transmitted Carrier Power, Transmitted carrier power of all codes not used for High Speed Physical Downlink Shared CHannel (HS-PDSCH) or High Speed Shared Channel Control CHannel (HS-SCCH) transmission, High Speed Downlink Shared CHannel (HS-DSCH) Required Power or High Speed Downlink Shared CHannel (HS-DSCH) Provided Bit Rate.
Based on this information the Node B and the Radio Network Controller (RNC) calculate resources that would be necessary if the user equipment is granted access to the cell with the reserved capacity necessary and estimates whether or not it is possible to accept the new user link.
The threshold for accepting the new user link could be different depending on whether it is a new call, a new service or whether there is only a handover done, and could depend on many other factors or information, such as the resource availability in the cell of the call or in the neighbouring cells. Typically, dropping an ongoing call is considered as more critical than the impossibility to initiate a call and the need to delay it until the resources are available.
It is possible that different transmission techniques are used by the Node B that are not activated when the admission control for a new service is considered, due to the fact that for instance when the user equipment (UE) tries to access the cell, the network can not know which techniques the user equipment (UE) is able to apply. Examples for such types of techniques are transmission (Tx) diversity or more generally Multiple-Input-Multiple-Output (MIMO).
Similarly the user equipment (UE) can use different receiver techniques for different channels which would imply different receiver performances and thus resources used. Whether the user equipment (UE) uses or supports one receiver technique or another one could even be transparent to the network, for instance in case the user equipment (UE) uses two different receive antennas.
Moreover, depending on the different receiver/transmitter techniques, the resources used by the user equipment (UE) can vary quite drastically. In particular, user equipments can use different receiver techniques that require more or less cell power for a same data rate. For example, user equipments can have a rake receiver, a Linear Minimum Mean Square Error (LMMSE) receiver or other types of receivers.
Currently, the Radio Network Controller (RNC) or Node B is only informed on the receiver techniques the user equipment (UE) uses and supports that impact the transmission techniques used in the RNC or Node B.